1. Field of the Invention
This invention relates to image and video displays, more particularly flat panel displays used as still image and/or video monitors, and methods of generating and driving image and video data onto such display devices.
2. Prior Art
Flat panel displays such as plasma displays, liquid crystal displays (LCD), and light-emitting-diode (LED) displays generally use a pixel addressing scheme in which the pixels are addressed individually through column and row select signals. In general, for M by N pixels—or picture elements—arranged as M rows and N columns, there will be M row select lines and N data lines. When a particular row is selected, N data lines are powered up to the required pixel voltage or current to load the image information to the display element. In a general active-matrix type LCD embodiment, this information is a voltage stored in a capacitor unique to the particular pixel (see FIG. 1). When the row and column signals de-select the pixel, the image information is retained on the capacitor. In a passive-matrix type LCD embodiment, rows and columns are arranged as stripes of electrodes making up the top and bottom metal planes oriented in a perpendicular manner to each other (see FIG. 2). Single or multiple row and column lines are selected with the crossing point or points defining the pixels which have the instantaneous video information. In such a case, either the row or column signal will have a voltage applied which is proportional to the pixel information. In a light-emitting-diode display type embodiment, the information is an instantaneous current passing through the pixel LED which results in the emission of light proportional to the applied current. Both active and passive matrix driving of LED arrays can be made. In all these display types mentioned, the pixel resolution is equal to or less than the geometric dimensions of the pixels. For example, in a VGA resolution screen, we need to implement at least 640×400 individual pixels for each color component. The total information conveyed to the display arrangement per video frame is then given as M×N×3×bit-width, where the factor 3 comes from the three basic colors constituting the image, i.e. red, green and blue, and the bit-width is determined from the maximum resolution of the pixel value. Most common pixel value resolution used for commercial display systems is 8 bits per color. For example, for a VGA resolution display, the total information needed to convey will be 640×400×3×8 equal to 6 Mbits per frame of image, which is refreshed at a certain frame refresh rate. The frame refresh rate can be 24, 30, 50, 60, etc. frames per second (fps). The faster rate capability of the screen is generally used to eliminate motion blurring, in which rates of 120 or 240 fps implementations can be found in commercial devices. For a gray-scale image, the information content is less by a factor of three since only the luminance information is necessary.
Video and still images are generally converted to compressed forms for storage and transmission, such as MPEG4, H.264, JPEG2000 etc. formats and systems. Image compression methods are based on orthogonal function decomposition of the data, data redundancy, and certain sensitivity characteristics of the human eye to spatial features. Common image compression schemes involve the use of Direct Cosine Transform as in JPEG or motion JPEG, or Discrete Walsh Transform. A video decoder is used to convert the compressed image information, which is a series of orthogonal basis function coefficients, to row and column pixel information to produce the image information, which will be for example at 6 Mbits per frame as in VGA resolution displays. However, from an information content point of view, much of this video information is actually redundant as the image had originally been processed to a compressed form, or it has information content in the higher order spatial frequencies to which the human eye is not sensitive. All these techniques pertain to the display system's components in the software or digital processing domain, and the structure of the actual optical display comprised of M×N pixels is not altered by any of the techniques used for the video format, other than the number of pixels and frame rate.
Spatial Light Modulators (SLM) are devices which alter the amplitude or phase, or both of a transmitted or reflected light beam in two-dimensions, thereby encoding an image to an otherwise uniform light illumination. The image pixels can be written to the device through electrical, or optical addressing means. A simple form of a spatial light modulator is the motion picture film, in which images are encoded on a silver coated film through photo-chemical means. An LCD system is also a particular kind of SLM, such that each pixel's information is encoded through electrical means to a specific position, and the backlit light source's spatial profile, which in general is uniform over the whole display area, is altered by the transmissivity of the pixels.
Prior art in the field generally addresses a single component of the problem at hand. For example, image compression and decompression techniques have not been applied directly on the display element, but only in transmission, storage, and image reconditioning and preparation of data for the display (as in U.S. Pat. No. 6,477,279). Systems incorporating spatial light modulation in which pixels are turned on and off to transmit a backlight to have various degrees of modulation can be implemented (eg. Multiple row select as in U.S. Pat. No. 6,111,560), or both backlight and image modulation can be used to enhance the resolution of the image (as in U.S. Published Application Nos. 2007/0035706 and US 2008/0137990). In especially the latter applications and their relevant disclosures, none of the image construction methods incorporate a temporal dimension in synthesizing the image frame, which is the subject of this disclosure. Thereby both systems, representative of conventional methods of displaying images pixel by pixel on a frame by frame basis, do not benefit from the inherent simplification of the interface and data throughput—which is embedded into the image compression process with which the video is transmitted in.
The present invention may have various modifications and alternative forms from the specific embodiments depicted in the drawings. These drawings do not limit the invention to the specific embodiments disclosed. The invention covers all modifications, improvements and alternative implementations which are claimed below.